1. Field of the Invention
The present invention relates to solar cells. In particular, the invention relates to methods and apparatuses for efficient packaging of solar cells for space applications.
2. Description of the Related Art
Photovoltaic cells, commonly called solar cells, are well-known devices which convert solar energy into electrical energy. Solar cells have long been used to generate electrical power in both terrestrial and space applications. Solar cells offer. several advantages over more conventional power sources. For example, solar cells offer a clean method for generating electricity. Furthermore, solar cells do not have to be replenished with fossil fuels. Instead, solar cells are powered by the virtually limitless energy of the sun. However, the use of solar cells has been limited because solar cells are a relatively expensive method of generating electricity. Nonetheless, the solar cell is an attractive device for generating energy in space, where low-cost conventional power sources are unavailable.
Typically, solar cells manufactured for space use have been of fairly small dimensions. Commonly, solar cells have had dimensions of 4 cmxc3x976 cm or less. In space applications, hundreds or thousands of the small solar cells are interconnected together to form large solar arrays. In a typical manufacturing process, a solar cell manufacturer delivers hundreds or thousands of separate, unconnected, solar cells to a solar array assembler. Often, the solar cell manufacturer mounts a coverglass over each cell to protect the cells against space radiation and other environmental conditions. Alternatively, the solar cell manufacturer may ship bare cells to the array assembler. The array assembler then must provide the coverglass. The array assembler also interconnects the individual cells into large, suitably sized panels.
The use of individual coverglasses for each cell has several disadvantages. For example, it is expensive and time consuming to mount a separate coverglass on each cell. In addition, the use of small cells incurs several disadvantages. For example, the smaller the cell size, the more cells are required to form an array of a given size. The more cells which must be assembled, the greater the manufacturing costs. In addition, each cell must be tested individually before being assembled into a larger array. Thus, the greater the number of cells required, the greater the number of tests which must be performed. Furthermore, the smaller the cells, the greater the total cell edge length (i.e. the length of all cell sides summed together) for a given array size. Cell edges are typically prone to damage. Thus, the greater the total edge length, the more likely that at least some cells will be damaged during the manufacturing, transport, and assembly of the cells.
One preferred embodiment of the present invention is a modular, glass covered solar cell array suitable for use in space. The modular, glass covered solar cell array includes at least physically and electrically interconnected solar cells. At least a portion of both cells are covered by a common, substantially transparent cover. The transparency of the cover will not substantially degrade when exposed to a space radiation environment. In one embodiment, at least one cell is comprised of single-crystal silicon. In another embodiment, at least one cell is comprised of GaAs. In yet another embodiment, at least one cell is comprised of multijunctions.
In one embodiment of the present invention, at least one cell has an area of at least 100 cm2. In another embodiment, at least-one cell is at least 150 xcexcm thick. In still another preferred embodiment, at least one cell is thinner than 150 xcexcm.
In another embodiment of the present invention, the solar array cells are interconnected by at least one conductor mounted on the backs of the cells. In still another embodiment, at least one cell has at least one contact for receiving the conductor. The contact wraps from a first side of the cell to a second side of the cell. In another embodiment, at least one cell has.at least one contact for interconnection to at least one other solar cell array.
In one embodiment, the solar cell array includes at least one bypass diode mounted to at least one surface of one of the cells. In another embodiment, the solar cell array includes contacts for connection to at least one externally mounted bypass diode.